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Studies of Incipient Combustion and Its Detection.

Authors

Hertzberg-M; Litton-CD; Garloff-R

Source

NTIS#: PB 263 903 :19 pages

Link

NIOSHTIC No.

10000357

Abstract

This Bureau of Mines report describes the results of a variety of studies of incipient combustion and its detection. Heated samples of coal, wood, and various polymers were used to evaluate the relative sensitivities of several types of detectors. The laboratory results indicate that submicrometer particulate detection is the most universal and sensitive method. Carbon monoxide detection was as sensitive as submicrometer particulate detection for pyrolyzing coal but was relatively insensitive to pyrolyzing wood or plastics. The conventional type of ionization smoke detector was the least sensitive for coal and of intermediate sensitivity for wood and plastics. Self-heating experiments with Pittsburgh seam coal piles of varying particle sizes gave ignition temperatures of 170 deg c for 4- to 7-um dust, which increased monotonically with particle size. The measured heating rates were compared with data from an adiabatic calorimeter to obtain preexponential rate constants. The propagation behavior of ignition waves and the overall self-heating appears to depend critically on the magnitude of the convective flows induced, which counteract the depletion of oxygen in the void spaces of the pile.